Reference · Vectors

vec.argsort

vec.argsort(list | null, bool=) -> list

What it does

The positions that would put a list of numbers in ascending order: vec.argsort([30, 10, 20]) is [1, 2, 0], since item 1 is the smallest. With true as the second argument the order is descending. Equal items keep their order. Index another list by these positions to sort it the same way, which is how to sort names by their scores.

Examples

print(vec.argsort([30, 10, 20]))print(vec.argsort([30, 10, 20], true))let xs = [30, 10, 20]print(vec.argsort(xs) | map((i) => xs[i]))

[1, 2, 0][0, 2, 1][10, 20, 30]

Edge cases

• Ties stay in their input order, ascending or descending: the sort is stable.
• The empty list, or null, gives the empty list.
• NaN sorts after every other number.
• Ints and floats mix.

print(vec.argsort([1, 1, 0]), vec.argsort([1, 1, 1], true))print(vec.argsort([]), vec.argsort(null))print(vec.argsort([float("nan"), 1, 2]))print(vec.argsort([2.5, 1, 2]))

[2, 0, 1] [0, 1, 2][] [][1, 2, 0][1, 2, 0]

Errors

An item that is not an int or a float, or an argument that is not a list, is a runtime error, not an error value. Strings are not sorted this way; use sort or sort_by.

print(vec.argsort(["b", "a"]))

line 1: `vec.argsort` expects a list of numbers, but item 0 is str

Chaining

The descending positions give a ranking; the first is the top:

let names = ["ann", "bob", "cy"]let scores = [71, 88.5, 64]print(vec.argsort(scores, true) | map((i) => names[i]))print(scores | vec.argsort(true) | first)

["bob", "ann", "cy"]1

See also

vec.argmin, vec.argmax, sort, sort_by, stats.rank

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